oneThis plural form is used for numbers like: 1
Every %1$d day
otherThis plural form is used for numbers like: everything else
Every %1$d days
Co %1$d dzień
Co %1$d dzień
Co %1$d dni
Every %1$d day
Every %1$d days
Every %1$d day
Every %1$d days
Co %1$d dzień
Co %1$d dzień
Co %1$d dni
%1$d - number